Tenontosaurus

Tenontosaurus ( ; ) is a genus of iguanodontian ornithopod dinosaur. It had an unusually long, broad tail, which like its back was stiffened with a network of bony tendons. The genus is known from the late Aptian to Albian ages of the Early Cretaceous period sediments of western North America, dating between 115 and 108 million years ago. It contains two species, Tenontosaurus tilletti (described by John Ostrom in 1970) and Tenontosaurus dossi (described by Winkler, Murry, and Jacobs in 1997). Many specimens of T. tilletti have been collected from several geological formations throughout western North America. T. dossi is known from only a handful of specimens collected from the Twin Mountains Formation of Parker County, Texas.

==History of discovery== The first Tenontosaurus fossil was found in Big Horn County, Montana by an American Museum of Natural History (AMNH) expedition in 1903. Subsequent digs in the same area during the 1930s, spearheaded by Barnum Brown and Roland T. Bird, unearthed 18 more specimens. Four more were recovered during the 1940s: two by a team from the University of Oklahoma, and two by a private collector, Al Silberling, operating on the behalf of Princeton University. Despite the large number of fossil specimens, the animal was not named or scientifically described during this time, though Barnum Brown gave it the informal name "Tenantosaurus", "sinew lizard", in reference to the extensive system of stiffening tendons in its back and tail.